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Discussion Starter · #1 ·
I've been working on my GL500 for a couple of years. I've had it running for the last year or so and start it up every few weeks. No problem, even in the cold of the winter. I recently took it in for a safety inspection, the last step before I licence and insure it. I had a list of minor issues which have mostly been corrected. The other day, after putting a spot of weld on the front steering stop; it was allowing the triple tree clamp to touch the tank on full lock left, I started the bike and it ran for a few seconds the cut out. It would not restart, even with a boost. I tried again today, no go. It gave a couple of hints of firing but only after prolonged cranking.



There is fuel in the tank and fuel came out when I loosened the left carb bowl drain plug. Even with a shot of starting ether the bike would not fire. There is spark from the plug wire to frame when I test for spark. The valves, at least on the left side are moving and there is compression on that side. I have fuel, spark and compression but something isn't right. Any ideas?
 

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I'd take a look at the wiring up near the head stock for anything that may have been disturbed during your welding. I was going to say check the kill switch, but I think you would not get spark if that were off. Check for ground connections, and possible shorts.
 

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What type of welder? Arc welding can destroy items like alternators on cars if they are connected during the work. Not saying this IS your problem but I'd carry out the relevent tests to at least rule this out as a cause.
 

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Discussion Starter · #5 ·
I used a MIG welder. The ground clamp was near the head stock. The battery still holds a charge and turns the engine over well. There is a healthy spark. I need to check the spark timing.
 

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Wait, do you not have compression on the left side? What is your air filter looking like, and have you modified the exhaust at all? These bikes need a very specific range of pressure in the airbox and exhaust to pull fuel/air correctly. I tried getting my bike to run with no filter for a really long time, then just threw the really bad filter back in and it fired right up. Filter out, no start. Filter back in, started right up.
 

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I'd take a look at the wiring up near the head stock for anything that may have been disturbed during your welding. I was going to say check the kill switch, but I think you would not get spark if that were off. Check for ground connections, and possible shorts.


I agree. Ground wires are not fused and can carry large amounts of current for a short period of time and heat up quickly. This melts insulation, especially inside wiring harnesses. This happened to me on an old car once. Good luck.
 

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Get a new set of plugs (cheap enough) and check for spark with the plugs (not the cables)grounded ( I wrap a copper wire from the plug threads)to the frame or engine (not the valve covers). If spark is evident at both plugs, reinstall and with the fuel petcock off, drain the carb bowls completely. With the carb inlets open (air box disconnected) spray some starting spray into each carb and crank it over (with the key in run). It should at least pop a few times, probably even run for a couple of seconds. If not, try it a couple of times. Doesn't take much starting spray. If you have spark, dry, good plugs, and some ether, it will run unless something mechanical has failed. A mechanical failure seems unlikely as you have been running it periodically and not disassembled the engine(correct, you have not disassembled the engine?). Timing is (substantially) fixed, problems only occur if it is assembled incorrectly. Having seen spark already, I would bet it's fuel related. Check the basics, the culprit is something simple. If you are getting spark, it cannot be a welding caused problem. If it still does not try to start, open both valve covers and look for valve train movement on both heads during cranking of the engine with the starter. Still okay? check for compression. If OK, go back to step one, something basic was overlooked. Get an experienced second opinion, 4 eyes are better than 2. These engines are "almost" bullet proof, it will run!
 

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Discussion Starter · #10 ·
Thanks Rich and others. I'll give your advice a try. I can't see it being an issue related to welding as I still get a spark. I'll check the right side as well for spark, valve movement and compression. If it isn't spark related then it must be timing or fuel related. I'll let you know how it turns out...and I will check the main fuse and the connections mentioned. Thanks for all the advice.
 

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Discussion Starter · #11 ·
I got home from work early today so I had a go at the bike. As per Rich's suggestion I pulled the plugs and checked for spark with the plug grounded. No spark! I waved the torch at the plugs and tried again. This time spark. Reinstalled the plugs and the bike started up right away. Thanks Rich!



PS. the plugs are new, save for the times I have been running the bike in the garage every now and then. Waiting on new clutch and brake levers before I take the bike back for reinspection.
 
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